The present invention relates generally to a welding apparatus and, more particularly, a portable welder having an electrical shield to prevent electrical arcing within the apparatus.
Portable welding units transportable to a work site are known. Typical of such known units include a lightweight enclosure consisting of a sheet metal material, such as aluminum or other metal and which metal enclosure has a front panel and a rear panel at the ends of the enclosure to contain the various components of the welder therein and also Includes a base that underlies the enclosure. In particular, such portable welding units or apparatus are, by nature, small, compact units that can be readily carried by and individual and may easily weigh less than 15 pounds. In the construction of such portable welders, therefore, it is necessary to install a large number of components, including the various electrical components, In a relatively small space in order to provide a fully functional welder having the features desired by the user while still constructing the unit to be compact and lightweight.
Accordingly, with such portable welding units, there are a considerable number of electrically conductive components that must be located in close proximity to each other. With welding apparatus, there are certain safety requirements that dictate the minimum spacing between electrical components in the apparatus to prevent arcing between conductive elements within the apparatus. Thus, with the portable welding apparatus, the problem is compounded by the need to keep the spacing to a minimum in order to assemble all of the necessary electrical and mechanical components within the required small volume of space within the outer enclosure.
As a further aggravation of the problem, there is a system that is utilized on a regular basis with large welding apparatus, in the TIG mode of operation, that is known as arc-starting and which provides a pulsed high voltage to a negative tungsten welding electrode for a predetermined period of time at the initiation of the welding process to better enable the striking of an arc between the welding electrode and the workpiece that is connected to a positive electrical source. While the presence of a high voltage is not particularly a problem in the large welding apparatus where the space is not at a premium, it is a considerable problem with the aforedescribed portable welding units since that high voltage can acerbate the problem of arcing within the portable welding apparatus simply due to the close proximity of the high voltage sources to other conductive surfaces.
In particular, with the arc starting feature, the voltage at the welding electrode and which is connected into a negative electrical receptacle externally provided in the welding apparatus, can reach 12,000 volts and therefore the internal stud that is located internal of the welding apparatus and which is connected to the exterior electrical receptacle also experiences that high voltage. Thus, in the interior of the welding apparatus, there is a potential high voltage site, that is, at the negative stud within that welding apparatus and, due to the extremely close quarters of the portable welding apparatus, the presence of the high voltage source can cause an arcing problem to occur within the apparatus itself. One of the more susceptible paths for that arcing is from the internal negative stud to the metal enclosure itself that surrounds the components of the welding apparatus; however, the problem obviously exists with respect to other electrically conductive components within the apparatus.
Therefore, it would be desirable to provide a portable welding apparatus that has the feature of arc starting available to the user but which also has protection in the form of shielding internal of the welding apparatus to prevent electrical arcing within the welding apparatus itself, thereby providing the advantage of portability along with the availability of the arc starting feature.